1. Field of the Invention
Embodiments of the invention generally relate to a method for transient testing of an oil well completed with an inflow control device (ICD), and more particularly, to a method for transient testing of an oil well completed with one or more ICDs, which determine reservoir and well parameters for deciding whether stimulation of the oil well would improve well productivity.
2. Description of the Related Art
Transient well testing provides an indirect determination of reservoir and well parameters for optimizing the productivity of an oil well. Transient testing is one of the most important tools in a spectrum of diagnostic tools used by petroleum engineers to characterize hydrocarbon assets and predict their future performance.
The long-term productivity of an oil well is influenced by many factors, including, for example, petrophysical or fluid properties of the oil, the degree of formation damage in the well and/or stimulation of the well, well geometry, well completion characteristics, the number of fluid phases in the wellbore, and the flow-velocity type of fluids through the wellbore.
When a well is drilled, it is preferred to have a positive differential pressure acting from the wellbore to the formation to prevent inflow of reservoir fluid. Consequently, some of the drilling fluid can penetrate the formation and particles suspended in the mud can partially penetrate pore spaces in the wellbore, reducing formation permeability and causing formation damage around the wellbore. Formation damage around the wellbore causes additional resistance to fluid flow through the wellbore, which can generate an additional pressure drop or loss of fluid flow into and through the wellbore, minimizing well productivity.
On the other hand, stimulation operations, for example, use of specifically designed fluids in a well can decrease the effect of the pressure drop in the near-wellbore region caused by the formation damage by improving the formation permeability around the wellbore. The impact of permeability impairment/improvement around the wellbore caused by drilling, production, and stimulation operations can be quantified in terms of a mechanical skin factor.
An ICD is a completion hardware device that has been deployed as a part of a well completion aimed at distributing the inflow of oil evenly through the well. Even though various designs have been used for the ICD, the principle for each ICD is the same—restrict fluid flow by creating an additional pressure drop that balances or equalizes the wellbore pressure drop caused by, for example, formation damage to achieve an evenly distributed flow profile along the length of the well. With a more evenly distributed flow profile, one can reduce, for example, water or gas coning, sand production, and address other drawdown-related production problems encountered in wells during production.
Conventional transient testing methods have been used to evaluate reservoir and oil parameters for determining whether a well completed with ICDs should be stimulated to improve the well's productivity. Conventional transient testing methods measure one or more production rates of the well to determine an apparent skin factor which is the summation of a well skin factor (i.e., representing a change in pressure [in the bore] caused by an altered region around the wellbore in comparison to an unaltered reservoir) and a completion skin factor (i.e., representing a pressure reading at a point in the production tubing downstream of the ICD or ICDs). Because these conventional transient testing methods are only able to determine the apparent skin factor as a summation of the well skin factor and the completion skin factor (i.e., does not distinguish between the individual well skin and completion skin factors), petroleum engineers are unable to specifically determine whether the well should be stimulated to improve the well's productivity.
Therefore, what is needed is a method for transient testing of an oil (or gas, as would be contemplated by one of ordinary skill in the relevant art) well completed with one or more ICDs, which determines the individual components of the mechanical skin factor (e.g., the respective well skin factor and the completion skin factor), so that an operator can determine from the well skin factor whether stimulation of the well would improve the well's productivity.